The AR-15 family of weapons is a popular firearm system. Many variants of the AR-15 rifle are currently offered. The AR-15 series firearms define a weapon that is composed of two major assemblies, an upper receiver and a lower receiver. The upper receiver includes the barrel group, the chamber, bolt and other parts. The lower receiver includes the trigger group, the buffer assembly, stock group and other parts. A market exists for incompletely/partially manufactured firearm lower receivers. A firearm lower receiver is unregulated until a minimum level of manufacturing is completed. This level is typically known as “80%”. Firearm lower receivers completed to this level are typically referred to as “80%” lower receivers. These firearms must then be completed by the end user to be operable. In a typical configuration the lower receiver is molded, cast, extruded and/or forged and is partially machined, with certain aspects of the inner slot (in which the trigger mechanism resides) remaining uncut. The finishing task cuts this remaining slot with appropriate dimensions and accuracy.
The completion of an 80% lower receiver utilizes a rotary power tool. These tools are typically, a drill, a router or a milling machine although other tools may suffice. A rotary tool is inserted into the rotary power tool and is rotated to remove material from the lower receiver.
The material removal locations have a maximum allowable rotary tool diameter to manufacture a functional lower receiver. Furthermore, the geometry of the lower receiver requires a minimum rotary tool length. These criteria are not ideal for the removal of material with a typical rotary tool. A rotary tool with a diameter and length capable of completing an operable lower receiver has poor rigidity and many drawbacks. Currently available rotary tools can experience any of a variety of problems including chatter, excessive deflection and catastrophic failure of the rotary tool shaft or cutter.
It would be desirable to provide a rotary tool to increase the quality, accuracy and longevity in the manufacturing and completion of lower receivers.